Fix FrozenElementListIterator.

tools/dom/templates/html/impl/impl_Element.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of html;
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements List {
   // Raw Element.
@@ skipping 371 matching lines @@
   }
 
   Element max([int compare(Element a, Element b)]) {
     return _Collections.maxInList(this, compare);
   }
 }
 
 class _FrozenElementListIterator implements Iterator<Element> {
   final _FrozenElementList _list;
   int _index = 0;
+  Element _current;
 
   _FrozenElementListIterator(this._list);
 
   /**
    * Moves to the next element. Returns true if the iterator is positioned
    * at an element. Returns false if it is positioned after the last element.
    */
   bool moveNext() {
     int nextIndex = _index + 1;
     if (nextIndex < _list.length) {
       _current = _list[nextIndex];
       _index = nextIndex;
       return true;
     }
     _index = _list.length;
     _current = null;
     return false;
   }
 
   /**
    * Returns the element the [Iterator] is positioned at.
    *
    * Return [:null:] if the iterator is positioned before the first, or
    * after the last element.
    */
-  E get current => _current;
+  Element get current => _current;
 }
 
 class _ElementCssClassSet extends CssClassSet {
 
   final Element _element;
 
   _ElementCssClassSet(this._element);
 
   Set<String> readClasses() {
     var s = new Set<String>();
@@ skipping 452 matching lines @@
 $if DART2JS
   // Optimization to improve performance until the dart2js compiler inlines this
   // method.
   static dynamic createElement_tag(String tag) =>
       JS('Element', 'document.createElement(#)', tag);
 $else
   static Element createElement_tag(String tag) =>
       document.$dom_createElement(tag);
 $endif
 }